1. Field of the Invention
The present invention relates to a rotary attenuator device.
2. Description of the Related Art
This type of device has been publicly known, for example as disclosed in Japanese Unexamined Patent Publication No. 2000-294410. This device has been often used as illustrated in the accompanied figure, FIG. 5, by arranging a plurality of devices 50 in one electronic device. Each rotary attenuator device 50 has a disk-shaped terminal board 52 which can rotate in a housing 51. The disk-shaped terminal board is driven by stepwise rotational movement for a specified angle through operating a dial (not illustrated) mounted at a driving shaft 53 which protrudes outside of the housing 51. Plural pairs of input and output terminals are locally arranged on one side of the terminal board 52. Also, an input coaxial connector 54 and an output coaxial connector 55 are provided on a side of the housing 52, which is opposite to the side where the driving shaft 53 is provided.
As illustrated in FIG. 6, contact shoes 56 and 57 respectively contact with input terminal 58 and output terminals 59 of a pair in the housing, and come to respectively contact with input terminals 58xe2x80x2 and output terminals 59xe2x80x2 of another pair once the terminal board rotates stepwise in one direction or another direction. Here, the contact shoes 56 and 57 are respectively connected to the central conductor of the connectors 54 and 55. The contact shoes 56 and 57 of the input and output coaxial connectors 54 and 55 are made similar each other.
As illustrated in FIG. 7, the contact shoe 56, for example, is made by bending a metal sheet band, such that the sheet surface of the bent part is parallel to the surface of the non-bent part. Therefore, it looks like a U-shape skid for the shaft 56A, which is connected to the central conductor. The contact shoe 54 extends along circumferential direction on the terminal board, e.g. a direction towards its adjacent input terminal 58xe2x80x2. The contact shoe 54 elastically contacts with the input terminal by its elasticity, and comes to contact with the adjacent input terminal with its rounded end, e.g. the rounded bottom part of the U-shape. Such contact shoe is also provided to the output coaxial connector.
As described above, in the publicly known device, since the pair of input and output terminals 58 and 59 respectively contact with the contact shoes 56 and 57 at one side of the terminal board, e.g. on the same side of the terminal board 52, the pair of the input and output terminals 58 and 59 cannot be provided too close to each other. Therefore, the input and output coaxial connectors 54 and 55 need to be arranged in more distant positions. Accordingly, the distance between the input terminal and the output terminal needs to be set relatively large. If plural pairs of both terminals are arranged along the circumference on the terminal board 52, the terminal board 52 becomes large. Consequently, if a plurality of the rotary attenuator devices 50 are arranged as illustrated in FIG. 5, the total width L becomes extremely large. That is, it is not avoidable that the electronic device, in which this rotary attenuator device is used, becomes even larger.
Moreover, since the possible elastic displacement of the conventional contact shoe of FIG. 7 is small, the allowable amount for errors in the displacement is small. In other words, it is hard to stabilize the contact. Furthermore, because of its shape, the contact shoe smoothly contacts with the terminal when the terminal board rotates in one rotational direction, but when the terminal board rotates in the opposite direction, the contact shoe is often caught by the terminal and also, the contact tends to be unstable.
Accordingly, it is an object of the present invention to provide a compact rotary attenuator which does not make the electronic device large when it is used in plural.
According to the invention there is provided a compact rotary attenuator which comprises the terminal board, on which plural pairs of input and output terminals are provided along its circumference and an electronic part including resistance are provided between the input and output terminals of each pair; the driving shaft which is joined to the center of the terminal board in the housing to be vertical to the surface of the terminal board and held so as to rotate; input and output contact shoes which elastically contact with input and output terminals of each pair by its freely sliding movement, and input and output coaxial connectors being held by the housing and having the central conductor extending to the inside of the housing.
In the rotary attenuator of the present invention, the first aspect of the invention is featured by that the input contact shoe and the output contact shoe are provided on different sides of the terminal board to contact with corresponding input terminal and output terminal.
According to the first aspect of the invention, since the input terminal and the output terminal are provided on the opposite side of the terminal board to the other, both can be arranged in adjacent position along the circumference of the terminal board, no matter with the size of its head portion. Therefore, the distance along the circumferential direction can be short when the plural pairs of the input terminal and the output terminal are arranged. Accordingly, the distance in a radial direction for the arrangement on the circuit board can be small. As a result, the terminal board can be small in its size, and also the attenuator device can be small in its size.
According to the present invention, it can be designed that the input contact shoe and the output contact shoe are provided at one end of a respective elastic arm, which is formed like a cantilever, extends in the radial direction of the terminal board, and contacts with the central conductor of the coaxial connector and held at the other end. By doing this, since the contact shoe extends in a radial direction of the terminal board, only the size of the contact shoe needs to be considered in a circumferential direction of the terminal board. There is no need to secure space for elastic arm to hold the contact shoe, and the distance between the terminals can be small. For those reasons, the device can be small in its size even on this point.
In the present invention, the housing has a pair of flat outer surfaces, which are parallel and face each other. If each axis of the driving shaft, the input coaxial connector and the output coaxial connector is supposed to be in a surface parallel to the pair of outer surfaces, a plurality of the attenuators can be arranged by contacting the outer surfaces together, so that total width can be made shorter.
The second aspect of the invention is featured by that the housing has the pair of flat outer surfaces, which are parallel and face each other. And all the axes of the driving shaft, the input coaxial connector and the output coaxial connector are in one surface parallel to the pair of the outer surfaces. Since all the axes of the driving shaft, the input coaxial connector and the output coaxial connector are in one surface parallel to the pair of the outer surfaces, the attenuator can be made even smaller than the one in the first invention. Therefore, the total width in a direction of arranging the attenuators become extremely small when plural attenuators are arranged. Therefore, the device, in which the attenuator is used, can be also designed to be smaller. It can be made that the input contact shoe and the output contact shoe are provided on one end of respective elastic arm, which is formed like a cantilever and extends in a radial direction of the terminal board. Here, the elastic arm is connected with the central conductor of the coaxial connector and held thereby.